Enhancement of polyimide adhesion on reactive metals

Abstract

In order to improve the adhesion of a polyimide layer to an underlying metal surface, an organic solution which cures to a silsesquioxane copolymer is applied to the surface. The polyimide and the copolymer are formed during a simultaneous curing step.

We claim: 
     
       1. A process for improving the adhesion of a polyimide layer to a metal surface, comprising the steps of: applying to said surface an organic solution, prepared by reacting an aminoalkoxysilane monomer, an arylalkoxysilane or arysilazane monomer and water in a solvent;   heating said surface under such conditions as to form a partially cured layer on said surface;   applying to said partially cured layer a solution comprising a polyimide precursor material; and   heating said surface under such conditions as to simultaneously form a layer of cured silsesquioxane copolymer, containing reactive amino groups which coordinate to said metal, and which passivates said metal and a polyimide layer.   
     
     
       2. The process of claim 1, wherein: said aminoalkoxysilane monomer is an aminotrialkoxysilane represented by the formula: ##STR2##  wherein: R 1  is a hydrogen atom; a saturated hydrocarbon residue or an amino-substituted, saturated hydrocarbon residue, having 1 to 5 carbon atoms; or an alkyl-substituted phenyl group or derivatives thereof, the alkyl group having 1 to 5 carbon atoms;   R 2  is a saturated hydrocarbon residue having 2 to 6 carbon atoms or an alkyl-substituted phenyl group, each alkyl group having 1 to 5 carbon atoms; and   R 3  is a saturated hydrocarbon residue having 1 to 8 carbon atoms;   or a mixture thereof; and   said arylalkoxysilane or arylsilazane monomer is represented by the formula, R 4  -Si-(Y) 3 , wherein R 4  is an unsubstituted or substituted aromatic residue and Y is (OR 6 ) or N(R 7 ) 2 , wherein R 6  is a saturated hydrocarbon residue having 1 to 5 carbon atoms and R 7  is a hydrogen atom or a saturated hydrocarbon residue having 1 to 5 carbon atoms.   
     
     
       3. The process of claim 2, wherein said reaction is carried out by employing a mole ratio of arylalkoxysilane monomer to aminoalkoxysilane monomer in the range from about 1:3 to about 4:1, and a mole ratio of water/total monomer in the range from about 0.5:1 to about 2:1. 
     
     
       4. The process of claim 3, wherein said reaction is carried out by employing a mole ratio of arylalkoxysilane monomer to aminoalkoxysilane monomer in the range from about 2:3 to about 2.5:1, and a mole ratio of water/total monomer in the range from about 0.9:1 to about 1.7:1. 
     
     
       5. The process of claim 2, wherein: said organic solution is prepared by first dissolving said arylalkoxysilane or arylsilazane monomer in said solvent, adding water, and then adding said aminoalkoxysilane monomer;   said solvent is selected from the group consisting of methanol, ethanol and isopropanol; and   said solution is allowed to age for a period of at least about 2 hours, before application to said substrate.   
     
     
       6. The process of claim 2, wherein said organic solution is prepared by reacting an aminoalkoxysilane monomer, an arylalkoxysilane or arylsilazane monomer, a tetraalkoxysilane monomer and water in a solvent. 
     
     
       7. The process of claim 6, wherein said tetraalkoxysilane monomer is tetraethoxysilane and is employed in a proportion of about 20 to about 45 percent based on the moles of total monomer. 
     
     
       8. The process of claim 2, wherein: said aminotrialkoxysilane monomer is represented by the formula: ##STR3##  wherein: R 1  is a hydrogen atom or a saturated hydrocarbon residue or an amino-substituted, saturated hydrocarbon residue, having 2 or 3 carbon atoms;   R 2  is a saturated hydrocarbon residue having 3 to 6 carbon atoms; and   R 3  is a saturated hydrocarbon residue having 1 to 4 carbon atoms;   or a mixture thereof; and   said arylalkoxysilane or arylsilazane monomer is represented by the formula, R 4  -Si-(Y) 3 , wherein R 4  is an unsubstituted or substituted phenyl group and Y is OR 6  or N(R 7 ) 2 , wherein R 6  is a saturated hydrocarbon residue having 1 to 4 carbon atoms, and R 7  is a hydrogen atom or a saturated hydrocarbon residue having 1 to 4 carbon atoms.   
     
     
       9. The process of claim 8, wherein said aminotrialkoxysilane monomer is selected from the group consisting of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane and N-β-(aminoethyl)-γ-aminopropyltriethoxysilane, and said arylalkoxysilane monomer is phenyltriethoxysilane. 
     
     
       10. The process of claim 1, wherein said surface is heated at a temperature from about 85° to about 150° C. for a period from about 0.5 to about 20 minutes to form said partially cured layer. 
     
     
       11. The process of claim 10, wherein said surface is heated at a temperature from about 90° to about 110° C. for a period from about 5 to about 10 minutes to form said partially cured layer. 
     
     
       12. The process of claim 1, wherein a solution comprising biphenylenedianhydride-p-phenylenediamine polyamic acid or ester is applied to said partially cured layer. 
     
     
       13. The process of claim 1, wherein a solution comprising pyromellitic dianhydride-oxydianiline polyamic acid or ester is applied to said partially cured layer. 
     
     
       14. The process of claim 1, wherein said simultaneous curing step is carried out at a temperature in excess of about 200° C. 
     
     
       15. The process of claim 14, wherein said simultaneous curing step is carried out at a temperature in excess of about 350° C. 
     
     
       16. The process of claim 1, wherein said metal is selected from the group consisting of copper, aluminum, silver, chromium, lead, tin, gold, titanium and tungsten. 
     
     
       17. A process for improving the adhesion of a polyimide layer to a semiconductor substrate containing a pattern of metallization, comprising the steps of: applying to said substrate an organic solution, prepared by reacting an aminoalkoxysilane monomer, an arylalkoxysilane or arylsilazane monomer and water in a solvent, wherein said aminoalkoxysilane monomer is represented by the formula: ##STR4##  wherein: R 1  is a hydrogen atom or a saturated hydrocarbon residue or an amino-substituted, saturated hydrocarbon residue, having 2 or 3 carbon atoms;   R 2  is a saturated hydrocarbon residue having 3 to 6 carbon atoms; and   R 3  is a saturated hydrocarbon residue having 1 to 4 carbon atoms;   or a mixture thereof;   said arylalkoxysilane or arylsilazane monomer is represented by the formula, R 4  -Si-(Y) 3 , wherein R 4  is an unsubstituted or substituted phenyl group and Y is OR 6  or N(R 7 ) 2 , wherein R 6  is a saturated hydrocarbon residue having 1 to 4 carbon atoms, and R 7  is a hydrogen atom or a saturated hydrocarbon residue having 1 to 4 carbon atoms; and   said reaction is carried out by employing a mole ratio of arylalkoxysilane monomer to aminoalkoxysilane monomer in the range from about 1:3 to about 4:1, and a mole ratio of water/total monomer in the range from about 0.5:1 to about 2:1;   heating said substrate at a temperature from about 85° to about 150° C. for a period from about 0.5 to about 20 minutes to form said partially cured layer;   applying to said partially cured layer a solution comprising a polyimide precursor material; and   heating said substrate at a temperature in excess of 200° C. to form a layer of cured silsesquioxane copolymer, containing reactive amino groups which coordinate to said metal, and which passivates said metal and a polyimide layer.   
     
     
       18. The process of claim 17, wherein said aminotrialkoxysilane monomer is selected from the group consisting of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane and N-β-(aminoethyl)-γ-aminopropyltriethoxysilane, and said arylalkoxysilane monomer is phenyltriethoxysilane. 
     
     
       19. The process of claim 18, wherein said substrate is heated at a temperature from about 90° to about 110° C. for a period from about 5 to about 10 minutes to form said partially cured layer; and said simultaneous curing step is carried out at a temperature in excess of about 350° C. 
     
     
       20. The process of claim 19, wherein said organic solution is prepared by reacting an aminoalkoxysilane monomer, an arylalkoxysilane or arylsilazane monomer, a tetraalkoxysilane monomer and water in a solvent. 
     
     
       21. The process of claim 20, wherein said tetraalkoxysilane monomer is tetraethoxysilane and is employed in a proportion of about 20 to about 45 percent based on the moles of total monomer. 
     
     
       22. A cured composite structure, comprising a metal, a polyimide layer, and a layer of silsesquioxane copolymer intermediate said metal and said polyimide layer, said copolymer being employed to improve the adhesion of said polyimide layer to said metal, said structure being produced according to the process of claim 1. 
     
     
       23. A cured composite structure, comprising a metal, a polyimide layer, and a layer of silsesquioxane copolymer intermediate said metal and said polyimide layer, said copolymer being employed to improve the adhesion of said polyimide layer to said metal, said structure being produced according to the process of claim 8. 
     
     
       24. A cured composite structure, comprising a metal, a polyimide layer, and a layer of silsesquioxane copolymer intermediate said metal and said polyimide layer, said copolymer being employed to improve the adhesion of said polyimide layer to said metal, said structure being produced according to the process of claim 9. 
     
     
       25. A semiconductor structure, comprising a substrate containing a pattern of metallization, a polyimide layer, and a layer of silsesquioxane copolymer intermediate said substrate and said polyimide layer, said copolymer being employed to improve the adhesion of said polyimide layer to said metal, said structure being produced according to the process of claim 17. 
     
     
       26. A semiconductor structure, comprising a substrate containing a pattern metallization, a polyimide layer, and a layer of silsesquioxane copolymer intermediate said substrate and said polyimide layer, said copolymer being employed to improve the adhesion of said polyimide layer to said metal, said structure being produced according to the process of claim 19. 
     
     
       27. A cured composite structure, comprising a metal, a polyimide layer, and a layer of silsesquioxane copolymer intermediate said metal and said polyimide layer, said copolymer containing reactive amino groups which coordinate to said metal, and which passivates said metal, said copolymer being employed to improve the adhesion of said polyimide layer to said metal. 
     
     
       28. A semiconductor structure, comprising a substrate containing a pattern of metallization, a polyimide layer, and a layer of silsesquioxane copolymer intermediate said substrate and said polyimide layer, said copolymer containing reactive amino groups which coordinate to said metal, and which passivates said metal, said copolymer being employed to improve the adhesion of said polyimide layer to said metal.